They may as well have said Heathrow instead of this announcement. By the very fact they've said that Cabinet members will be allowed to voice their own opinions and not necessarily support the overall decision, which they usually must do as part of Cabinet collective responsibility, it can only be Heathrow. None of the Cabinet are opposed to Gatwick, but we know Boris and Justine Greening are both strongly opposed to Heathrow.
Why on earth they think kicking this out a week will make a difference. Maybe the Witney by-election taking place today. Just more dithering. Yes it's a decision that not everyone will like, but that's why you're elected into Government.